Automatic reclosing circuit-breaker system



Oct. 22, 1929. o. c. TRAVER AUTOMATIC RECLOSING CIRCUIT BREAKER SYSTEMFiled May 22, 1926 InVefibOr': Oliver" QTr-aver";

5 His Attorneg.

Patented Oct. 22, 1929 UNITED STATES PATENT OFFICE comramr, aconrona'rron or NEW Yo AUTOMATIC BECLOSING CIRCUIT-BREAKER SYSTEIApplication filed Kay 22,

the reclosure of a circuit breaker when either of the circuits, whichthe circuit breaker connects together, is energized and the load connected to the other circuit isnormal.

Another object of my invention is to provide an automatic reclosingcircuit breaker system for connecting two electric circuits toget-herwhen either of the two circuits are energized and a predeterminedstub-end feed condition or a predetermined multiple feed '20 conditionexists on the other circuit.

My invention will be better understood from the following description,taken "in connection with the accompanying drawing, and its scope willbe pointed out inthe appended claims.

In the accompanyingdrawing, which diagrammatically shows an automaticreclosing circuit breaker system embodying my invention, 1 represents acircuit breaker which is arranged to connect together the conductors 2and 3 of two electric circuits. In order to simplify the drawing, it hasbeen assumed that the ground constitutes the other side of each of thetwo circuits, but it is evident that my invention is not limited togrounded circuits, butis applicable to any electric system. The circuitcomprisin the conductor 2 and the ground is adapte to be supplied by asuitable source 4 and the circuit comprising the conductor 3 and theground is adapted to be supplied by a suitable source 5. As shown in thedrawing, the circuit breaker 1 is a contactor having a coil 6, whichwhen energized maintains the circuit breaker in its closed position.However, it is evident that any other type of circuit breaker, examplesof which are well known in the art, may be used. The circuit of the coil6 includes contacts 7 of an overload relay 8, the coil 9 of which is1926. Serial No. 111,068.

so connected that it is ener zed in accordance with the current flowingthrough the main contacts of the circuit breaker 1 when it is closed. Asshown, the coil 9 is connected in series with the conductors-2 and 3.The relay 8 is designed so that it opens its contacts when the currentthrough the coil 9 exceeds a predetermined value. The relay 8 operatesirrespectively of the direction of current through its winding so thatit operates upon the occurrence of an abnormal load on either of the twocircuits to efl'ect the opening of the circuit breaker 1.

After the circuit breaker 1 has been opened by an abnormal loadcondition on either of the two circuits, it is desirable to have thecircuit breaker'reclosed as soon as feasible after the abnormalcondition has been-removed. It is well known in the art, however, that,in order for the reclosing equipment to control properly the reclosingof the clrcuit breaker, it is necessary to have the circuit breakerreclose in response to one electric condition of the abnormal circuitwhen it is not being energized independentl of the normal circuit, i.e., under stub-end eed conditions,

and to be reclosed in response'to another electric condition of theabnormal circuit when it is being energized independently, i. e., undermultiple feed conditions.

For accomplishing the above results, I provide a load indicatingresistor 10 which is arranged to be connected in series with theconductor 2 and 3 when the circuit breaker is open so as to limit to arelatively small value t e amount of current that flows from the normalcircuit into the abnormal circuit; a reclosing relay 11 for controllinthe reclosing of the circuit breaker 1 un er stub-end feed conditions ofthe abnormal circuit, a reclosing relay 12 for controlling the reclosinof the circuit breaker 1 under multiple fee conditions of the abnormalcircuit; a selective relay 13 which determines which of the tworeclosing relays controls the-reclosing, and .a

' transfer rela 14 for controlling theconnections of the c osing coil sothat it is completed across whichever circuit is energized when thecircuit breakeris open and only one of the circuits is independentlyenergized.

The reclosingrelay 11 is connected and arranged in such a manner that itis controlled in accordance with the sum of and the difference betweenthe voltages of the two circuits, and operates irrespectively of 'whichside .has the faulty condition convoltage across the circuit comprisingtheconductor 2 and ground, and the coils 17 and 19 are connected in anysuitable manner so that they are energized in accordance with thevoltage across the circuit comprising the conductor 3 and ground. Asshown in the drawing, coils 16 and 18 are arranged 6'59 connected inseries between conductor 2 and ground and coils 17 and 19 are arrangedto be connected in series between conductor 3 and ground when theselective relay contacts 21 are closed. The coils 16 and 17 are shownwound around the same core and are arranged accumulatively so that thecombined eflect thereof varies as the sum of the voltages of the twoelectric circuits. The coils 18 and 19 are shown wound around theopposing core and are arranged differentially so that the combinedeffect thereof varies as the difference between the voltages of the twoelectric circuits. The coils 16 and 17 are arranged to close the relaycontacts 20 when the difference between the sum of and the differencebetween the voltages of the two circuits is greater than a certainamount.

It will be observed that by my arrangement of windings the relayoperates irrespectively of which side has the abnormal condition, sincewith a given voltage on either side and another given voltage on theother, the sum of the voltages, the difference betweenthe voltages andthe difference between the sum and difference are the same in bothcases. For example, if one circuit has 300. volts across it, and theother has 20 volts across it, or vice versa, the sum is always 320volts, the difference is always 280, and the difference between the sumand difference, whichis the value in response to which the relay 11operates, is always volts.

The contacts 20 of the reclosing relay 11' are in a circuit for closingcoil 6 which also includes the contacts 21 of the selective reranged inany suitable manner so that its contacts 21 are closed only understub-end feed conditions of the faulty circuit. As

close its contacts 22, which are in another circuit for the closing coil6, under certain multiple feed conditions of the faulty circuit. Asshown, the coil of the relay 12 is connected in parallel with the coilof the selective relay 13, but the relay 12 is designed to open itscontacts 22 in response to a much lower difference in voltage betweenthe two electric circuits than the difference required to pick up therelay 13. Under multiple feed conditions of the faulty circuit, thevoltage across the faulty circuit is much higher for a given load thanunder stub-end feed conditions, so that the selective relay 13 is notsufficiently energized to close its contacts 21. Therefore, the relay 11cannot effect the closing of the circuit of the closing coil 6. As theabnormal condition on the faulty circuit is removed, the voltage of thefaulty circuit increases so that voltage impressed upon the winding ofthe relayv 12 decreases. At a predetermined value, the relay 12 closesits contacts 22 and completes the circuit for the closing coil 6.

It will be observed that the relays 12 and 13 are so connected andarranged that their operation is the same irrespective of which circuithas the abnormal load condition connected thereto.

The coil of the transfer relay 14 is arranged to be connected betweenthe conductor 3 and ground by auxiliary contacts 24 on the circuitbreaker 1 when it is in its open position. If the voltage betweenconductor 3 and ground is approximately normal, the relay 14 3 andground after the breaker opens, relay '14 remains in the posit-ionshown, in which position its contacts 26 connect the closing coil 6 sothat'its circuits are completed between conductor 2 and ground-Therefore, by means of relay 14, the closing coil 6 always hasapproximately normal voltage impressed thereon during the closingoperation.

Any suitable means, examples of which are well known in the art, may beprovided for preventing the circuit breaker from being reclosed within acertain length of time after the breaker opens. As shown in the drawing,this result is obtained by means of a dashpot 23 which prevents theoverload relay from closing its contacts? until a predetermined timeafter the circuit breaker opens.

The operation of the system shown is as follows: So long as the circuitbreaker is closed and there are normal loads connected to both circuits,the circuit breaker 1 remains closed. The circuit of the closing coil 6is from conductor 2 through resistor 31, contacts 26 of relay 14,closing coil 6, overload relay contacts 7, contacts 22 of the relay 12,to ground.

When an overload occurs on either circuit which is sufficient to causethe overload relay 8 to open its contacts 7, the coil 6 is deenergizedand the circuit breaker 1 opens. If the abnormal condition is betweenconductor 3 and ground, the transfer relay 14 does not pick up when itscircuit is completed by the auxiliary contacts 24 on the circuitbreaker. If the abnormal condition is between conductor 2 and ground,and the source 5 is in service, relay 14 is sufficiently energized, whenits circuit is completed, to open its contacts 26 and close its contacts25. A

predetermined time after the circuit breaker opens, the overload relayrecloses' its contacts 7 inthe circuit of the closing coil 6.

Let it be assumed that the abnormal condition occurs between conductor 3and ground so that the relay 14 does not pick up. If the source 5 is notin service when the circuit breaker 1 opens, the voltage across thecircuit comprising conductor 3 and ground is very low, so thatsubstantially normal voltage is impressed upon the coils of relays 12and 13. Both of these relays pick up, so that the contacts 22 are openedand the contacts 21 are closed. If, however, multiple feed conditionsexist on the faulty circuit after the breaker opens, that is, the source5 is connected thereto, there is sufficient voltage across thefaultycircuit so that only the relay 12 picks up. The relay 13 maintains itscontacts 21 open so that the stub-end reclosing relay cannot effect thereclosing of the circuit breaker.

conditions exist on the faulty circuit, that is, the source 5 is-not inservice, so that relay 13 closes its contacts 21 and thereby connectscoils 16 and 18- between conductor 2 and ground, and connects coils 17and 19 between conductor 3 and ground. After the circuit breaker opens,a very small current is supplied from the source 4 through resistor 10.to the faulty circuit. This small current produces a voltage dropacross the load circuit and this voltage drop varies with the resistanceof the load. Therefore, as the load resistance varies, the voltageimpressed upon the coils 17 and 19 of the stub-end reclosing relayvaries accordingly. So long as the re- First it will be assumed thatstub-end feedsistance of the load across the fault circuit I is lessthan a certain value, the pul exerted by the coils 16 and 17 is notsufficient to close the contacts 20 of the relay 11 against the biasofvthe spring 40 and the pull exerted by the coils 18 and 19. As theload resistance increases, the combined force exerted by the coils 16and 17 increases, and the combined force exerted by the coils l8 and 19decreases. When the load resistance increases to such a value that thedifference between these two combined forces is more than a certainvalue, the relay contacts 20'are closed and a circuit is completed forthe closing'coil 6 of the 'circuit breaker from the conductor 2, throughcontacts 26 of the transfer relay 14, closing coil 6, overload relaycontacts 7, contacts 20 of reclosing relay 11, contacts 21 of selectiverelay 13 to ground. When the circuit breaker closes, its main contactsshort circuit the coil of relay 12 so that its contacts 22 are closedand complete the heretofore described holding circuit for the closingcoil 6 to maintain the circuit breaker in its closed position. The maincontacts of the circuit breaker also short circuit the coil of the relay13, which is restored to the position shown in the drawing. The openingof the contacts 21 effects the opening of the circuits of the coils ofthe reclosing relay 11 so that the spring 40 restores the relay to theposition. shown.

If the source 5 is connected to the faulty circuit when the circuitbreaker 1 opens, the relay 12 picks up and opens its contacts 22, butrelay 13 does not pick up so that the reclosing relay 11 is inoperativeto effect the reclosing of the circuit breaker. So long as the load issuch that the'voltage difference between the two circuits is more than acertain value, the relay l2 maintains its conconductor 2 throughcontacts 26 of transfer relay 14, closing coil 6, overload relaycontacts 7 contacts 22 of reclosing relay 12 to ground. Afterthe circuitbreaker closes, the

various control devices are restored to their normal condition in themanner heretofore described,

It will be obvious from the drawing and the above description that thereclosing equipment operates in the same manner when the fault isbetween conductor 2 and ground and the circuit comprising conductor 3and ground is energized by source 5, except that relay 14 is picked upby the opening of the circuit breaker so. that the closing coil 6 isconnected between conductor 3 and .ground during the closing operation.As soon as circuit breaker 1 closes, the relay 14 is restored to itsnormal position so that the closing coil is reconnected betweenconductor 2 and ground.

In order to prevent the closing coil 6 from being momentarilydeenergized while the transfer relay is moving from its energized to itsdeenergized position, the relay 14 may be designed in any suitablemanner, so that its contacts 26 are closed before the contacts 25 areopened. 'With such an arrangement. however, the conductors 2 and 3 areconnected together for an instant, through the contacts 25 and 26 of therelay 14. In order to limit the current, that flows from one conductorto the. other through this momentarily closed circuit, to a value withinthe capacity of the contacts 25 and 26, suitable current limiting meansmay be provided therein. As shown in the drawing, this result isobtained by means of a resistor 30 connected between the conductor 3 andthe contacts 25, and a similar resistor 31 is connected between theconductor 2 and the contacts 26. It is evident, however, that either oneof these resistors may be omitted, provided the resistor which is leftis such as to limit the current to the desired value.

IVhile I have, in accordance with the provisions of the patent statutes,shown and described my invention as applied to a particu lar system, andas embodying various devices diagrammatically indicated, changes andmodifications will be obvious to those skilled in the art, and I,therefore, aim in the appended claims to cover all such changes andmodifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. In an automatic reclosing circuit breaker system, two electriccircuits, a circuit breaker connecting said circuits together, means foreffecting the opening of said circuit breaker, and means controlled inaccordance with the sum of and the difference between the voltages ofthe two circuits for I effecting the reclosing of the circuit breaker.

2. In an automatic reclosing circuit breaker system, two electriccircuits, a circuit breaker'connecting said circuits together, means foreffecting the opening of said 011- cuit breaker, and means responsive toa pre- .determined difference between the sum of cuits and to exert anopposing force in accordance with the difference between the voltages ofthe two circuits.

4. In an automatic reclosing circuit breaker system, two electriccircuits, a circuit breaker connecting said ciruits together, means foreffecting the opening of said circuit breaker, and a balance relay foreffecting the reclosure of said circuit breaker comprising a pivotedmember, two coils respectively connected across said electric circuitsand arranged to exert a force which tends to move said member in onedirection and which varies in accordance with the sum of the voltages ofthe two circuits, and two other coils respectively connected across saidelectric circuits and arranged to exert a force which tends to move saidmember in the opposite direction and which varies in accordance with thedifference between the voltages of said circuits.

5. In an automatic reclosing circuit break er system, two electriccircuits, a circuit breaker connecting said ciruits together, means foreffecting the opening of said circuit breaker when a'predeterminedabnormal condition occurs on either of said circuits and means foreffecting the reclosure of said circuit breaker when the abnormalcondition has been removed from the faulty circuit and the other circuitis energized including a current limiting device arranged to beconnected between said circuits when the circuit breaker is open,

and a relay controlled in accordance with the a sum of and thedifference between the voltages of the two circuits.

6.- In an automatic reclosing circuit breaker system, two electriccircuits, a circuit breaker connecting said ciruits together, means foreffecting the opening of said circuit when a predetermined abnormalcondition occurs on either of said circuits, and means for effecting thereclosure of said circuit breaker when the abnormal condition has beenremoved from the faulty circuit and the other circuit is energizedincluding a current limiting device arranged to be connected betweensaid circuits when the circuit breaker is open and a differential relayhaving a pivoted member, two coils connected across one of said circuitsso as to be energized in accordance with the voltage thereof and twocoils connected across the other of said circuits so as to be energizedin accordance with the voltage thereof, one

of said first mentioned two coils being arranged with one of said secondmentioned two coils so that they exert a combined force on said pivotedmember which tends to move it in one direction and which varies inaccordance with the sum of the voltages of the two circuits and theother two of said coils being arrangedso that they exert a combinedforce on 'said pivoted member which tends to move it in the oppositedirection and which varies in accordancewith the difference between thevoltages of the two cit-cuits.

7 In an automatic reclosing circuit breaker system wherein a circuitbreaker 1s arranged to connect a source of current to a circuit understub-end and multiple -feed conditions thereof, the combination of meanscontrolled by an electrical condition of said circuit for effecting thereclosure of the circuit breaker under multiple feed conditions thereof,means for supplying a limited current to said circuit from said sourcewhen the circuit breaker is open, and means controlled in accordancewith the sum of and the difference between the voltages of the sourceand said circuit for effecting the reclosure'of the circuit breakerunder stub-end feed conditions of said circuit.

8. In an automatic reclosing circuit breaker system wherein a circuitbreaker is arranged to connect a source of current to a circuit understub-end and multiple feed conditions thereof, the combination of meanscontrolled by an electrical condition of the circuit for effecting thereclosure of the circuit breaker under multiple feed conditions of theload circuit, means for supplying a limited current to said circuit fromsaid source when said circuit breaker is open, means controlled inaccordance with the sum of and the difference between the voltages ofthe source and said circuit for effecting the reclosure of the circuitbreaker under stub-end feed conditions of said circuit, and meanscontrolled b the voltage across said circuit for determining which ofsaid reclosing means is to effect the reclosing of the circuit breaker.

9. In an automatic reclosing circuit breaker system wherein a circuitbreaker is arranged to connect a source of current to a circuit understub-end and multiple feed conditions thereof, the combination of meanscontrolled by an electrical condition of the circuit for effecting thereclosure of the circuit breaker under multiple feed conditions of thecircuit,

7 means for supplying a limited current to said circuit from said sourcewhen said circuit .breaker is open, means responsive to a predetermineddifference between the sum of and the difference between the voltages ofthe source and the circuit for effecting the reclosure of the circuitbreaker under stub-end feed conditions of the circuit, and meansresponsive to the difference between the voltages of the source and thecircuit for rendering said stub-end reclosing means operative.

10. In an automatic reclosing circuit breaker system, two electriccircuits, a circuit breaker connecting said' circuits together, meansresponsive to an abnormal condition on either circuit for effecting theopening of v circuits for effecting the reclosing of said cirvoltagedifference between the two circuits exceeds a predetermined value.

11. In an automatic reclosing circuit breaker system, twoielectriccircuits, a circuit breaker for connecting said circuits together, aclosing coil for said circuit breaker, a circuit for said closing coil,means responsive to the difference between the voltages of said electriccircuits for effecting the completion of said closing coil circuit whensaid voltage difference is below a predetermined value, a second circuitfor said closing coil, contacts in said second circuit, means responsiveto a predetermined difference between the sum of and the differencebetween the voltages of the two circuits for effecting the closing ofcertain of said contacts when said last mentioneddifference is more thana certain value, and means responsive to the difference between thevoltages of the two electric circuits for effecting the closing of theother of said contacts when the voltage difference between said twoelectric circuits exceeds a predetermined value. y

In witness whereof, I have hereunto set my hand this 21st day of May,1926.

I OLIVER C. TRAVER.

said circuit breaker, means responsive to the difference between thevoltages of said circuits for effecting the reclosure of said breakerwhen said voltage difference is below a predetermined value, meansresponsive to a predetermined difference between the sum of and thedifference between the voltages of thetwo

